The OLED (Organic Light-Emitting Diode) display panel has the advantages of wide color gamut, high contrast, energy saving, and foldability such that the OLED has strong competitiveness in the display of the new era. The AMOLED (Active-matrix organic light-emitting diode) display technology is one of the key development directions of flexible display. The basic driving circuit of the AMOLED display is 2T1C, which includes a switching thin-film transistor, a driving thin-film transistor and a storage capacitor Cst. Since the threshold voltage Vth of the driving thin-film transistor is easily drifted, the driving current of the OLED is fluctuated, which causes a defect in the OLED display panel and affects image quality. In order to improve the display quality, various companies have proposed several kinds of pixel compensation circuits. FIG. 1 and FIG. 2 are respectively a pixel compensation circuit and an operation timing of the pixel compensation circuit. It is divided into three operational phases:
The first phase: the scanning signal S(n−1) is set at a low voltage level, the thin-film transistors T4 and T7 are turned on, and the gate of the driving thin-film transistor T1 and the voltage level of the anode of the OLED are reset to VI.
The second phase: the scanning signal S(n) is set at a low voltage level, the thin-film transistors T2 and T3 are turned on, and the voltage level of the gate of the driving thin-film transistor T1 is Vdata-Vth, wherein Vdata is the voltage of the data signal, and Vth is the threshold voltage of the driving thin-film transistor T1.
The third phase: the enable signal EM(n) is set at a low voltage level and the OLED is illuminated.
In the second phase, T1, T2, and T3 are all turned on, and T4, T5, and T6 are all turned off. At this time, the data signal charges the gate of T1 through the T1, T2, and T3. When the voltage level of the gate of T1 rises to Vdata-Vth, T1 is turned off, and the voltage level of the gate of T1 is no longer rising.
However, in a high scanning frequency, high resolution display panel, the charging time of each row of pixels is shorter, and the charging of the data signal to T1 will be slower and slower in the later phase such that the gate of T1 is difficult to be charged to an expected voltage in a short period of time, and there is a problem that the charging is not full in one frame time, and the corresponding OLED cannot be normally illuminated, which affects the display quality of the display panel under dynamic pictures and the like.
On the other hand, in the existing black insertion technique, by adjusting the period of the high voltage level of the light-emitting signal EM(n) (when the light-emitting signal EM(n) is high, T5 and T6 are turned off, no current flows through the OLED, so that the OLED does not emit light during this period) at the low grayscale level (for example, grayscale levels below 128 grayscale level), the light-emitting time in one frame of the OLED display panel is reduced. However, when the light-emitting signal EM(n) is at a high voltage level, T1 still operates normally in the saturation region, which reduces the lifetime of the entire pixel compensation circuit.